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useNumericLiterals

src/content/docs/linter/rules/use-numeric-literals.mdx

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import { Tabs, TabItem } from '@astrojs/starlight/components';

<Tabs> <TabItem label="JavaScript (and super languages)" icon="seti:javascript"> ## Summary - Rule available since: `v1.0.0` - Diagnostic Category: [`lint/complexity/useNumericLiterals`](/reference/diagnostics#diagnostic-category) - This rule is **recommended**, meaning it is enabled by default. - This rule has a [**safe**](/linter/#safe-fixes) fix. - The default severity of this rule is [**warning**](/reference/diagnostics#warning). - Sources: - Same as [`prefer-numeric-literals`](https://eslint.org/docs/latest/rules/prefer-numeric-literals)

How to configure

json
{
	"linter": {
		"rules": {
			"complexity": {
				"useNumericLiterals": "error"
			}
		}
	}
}

Description

Disallow parseInt() and Number.parseInt() in favor of binary, octal, and hexadecimal literals

JavaScript provides literal forms for binary, octal, and hexadecimal numbers. For example: 0b11, 0o77, and 0xff. Using the literal forms enable static code analysis and avoid unnecessary computations.

Examples

Invalid

js
parseInt("111110111", 2);
<pre class="language-text"><code class="language-text">code-block.js:1:1 <a href="https://biomejs.dev/linter/rules/use-numeric-literals">lint/complexity/useNumericLiterals</a> <span style="color: #000; background-color: #ddd;"> FIXABLE </span> ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ <strong><span style="color: Orange;">⚠</span></strong> <span style="color: Orange;">This call to </span><span style="color: Orange;"><strong>parseInt()</strong></span><span style="color: Orange;"> can be replaced by a binary literal.</span> <strong><span style="color: Tomato;">&gt;</span></strong> <strong>1 │ </strong>parseInt(&quot;111110111&quot;, 2); <strong> │ </strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong> <strong>2 │ </strong> <strong><span style="color: lightgreen;">ℹ</span></strong> <span style="color: lightgreen;">Using a literal avoids unnecessary computations.</span> <strong><span style="color: lightgreen;">ℹ</span></strong> <span style="color: lightgreen;">Safe fix</span><span style="color: lightgreen;">: </span><span style="color: lightgreen;">Use the computed binary literal instead.</span> <strong>1</strong> <strong> │ </strong><span style="color: Tomato;">-</span> <span style="color: Tomato;"><strong>p</strong></span><span style="color: Tomato;"><strong>a</strong></span><span style="color: Tomato;"><strong>r</strong></span><span style="color: Tomato;"><strong>s</strong></span><span style="color: Tomato;"><strong>e</strong></span><span style="color: Tomato;"><strong>I</strong></span><span style="color: Tomato;"><strong>n</strong></span><span style="color: Tomato;"><strong>t</strong></span><span style="color: Tomato;"><strong>(</strong></span><span style="color: Tomato;"><strong>&quot;</strong></span><span style="color: Tomato;"><strong>1</strong></span><span style="color: Tomato;"><strong>1</strong></span><span style="color: Tomato;"><strong>1</strong></span><span style="color: Tomato;"><strong>1</strong></span><span style="color: Tomato;"><strong>1</strong></span><span style="color: Tomato;"><strong>0</strong></span><span style="color: Tomato;"><strong>1</strong></span><span style="color: Tomato;"><strong>1</strong></span><span style="color: Tomato;"><strong>1</strong></span><span style="color: Tomato;"><strong>&quot;</strong></span><span style="color: Tomato;"><strong>,</strong></span><span style="color: Tomato;"><span style="opacity: 0.8;"><strong>·</strong></span></span><span style="color: Tomato;"><strong>2</strong></span><span style="color: Tomato;"><strong>)</strong></span><span style="color: Tomato;">;</span> <strong>1</strong><strong> │ </strong><span style="color: MediumSeaGreen;">+</span> <span style="color: MediumSeaGreen;"><strong>0</strong></span><span style="color: MediumSeaGreen;"><strong>b</strong></span><span style="color: MediumSeaGreen;"><strong>1</strong></span><span style="color: MediumSeaGreen;"><strong>1</strong></span><span style="color: MediumSeaGreen;"><strong>1</strong></span><span style="color: MediumSeaGreen;"><strong>1</strong></span><span style="color: MediumSeaGreen;"><strong>1</strong></span><span style="color: MediumSeaGreen;"><strong>0</strong></span><span style="color: MediumSeaGreen;"><strong>1</strong></span><span style="color: MediumSeaGreen;"><strong>1</strong></span><span style="color: MediumSeaGreen;"><strong>1</strong></span><span style="color: MediumSeaGreen;">;</span> <strong>2</strong> <strong>2</strong><strong> │ </strong> </code></pre>
js
Number.parseInt("767", 8);
<pre class="language-text"><code class="language-text">code-block.js:1:1 <a href="https://biomejs.dev/linter/rules/use-numeric-literals">lint/complexity/useNumericLiterals</a> <span style="color: #000; background-color: #ddd;"> FIXABLE </span> ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ <strong><span style="color: Orange;">⚠</span></strong> <span style="color: Orange;">This call to </span><span style="color: Orange;"><strong>Number.parseInt()</strong></span><span style="color: Orange;"> can be replaced by an octal literal.</span> <strong><span style="color: Tomato;">&gt;</span></strong> <strong>1 │ </strong>Number.parseInt(&quot;767&quot;, 8); <strong> │ </strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong> <strong>2 │ </strong> <strong><span style="color: lightgreen;">ℹ</span></strong> <span style="color: lightgreen;">Using a literal avoids unnecessary computations.</span> <strong><span style="color: lightgreen;">ℹ</span></strong> <span style="color: lightgreen;">Safe fix</span><span style="color: lightgreen;">: </span><span style="color: lightgreen;">Use the computed octal literal instead.</span> <strong>1</strong> <strong> │ </strong><span style="color: Tomato;">-</span> <span style="color: Tomato;"><strong>N</strong></span><span style="color: Tomato;"><strong>u</strong></span><span style="color: Tomato;"><strong>m</strong></span><span style="color: Tomato;"><strong>b</strong></span><span style="color: Tomato;"><strong>e</strong></span><span style="color: Tomato;"><strong>r</strong></span><span style="color: Tomato;"><strong>.</strong></span><span style="color: Tomato;"><strong>p</strong></span><span style="color: Tomato;"><strong>a</strong></span><span style="color: Tomato;"><strong>r</strong></span><span style="color: Tomato;"><strong>s</strong></span><span style="color: Tomato;"><strong>e</strong></span><span style="color: Tomato;"><strong>I</strong></span><span style="color: Tomato;"><strong>n</strong></span><span style="color: Tomato;"><strong>t</strong></span><span style="color: Tomato;"><strong>(</strong></span><span style="color: Tomato;"><strong>&quot;</strong></span><span style="color: Tomato;"><strong>7</strong></span><span style="color: Tomato;"><strong>6</strong></span><span style="color: Tomato;"><strong>7</strong></span><span style="color: Tomato;"><strong>&quot;</strong></span><span style="color: Tomato;"><strong>,</strong></span><span style="color: Tomato;"><span style="opacity: 0.8;"><strong>·</strong></span></span><span style="color: Tomato;"><strong>8</strong></span><span style="color: Tomato;"><strong>)</strong></span><span style="color: Tomato;">;</span> <strong>1</strong><strong> │ </strong><span style="color: MediumSeaGreen;">+</span> <span style="color: MediumSeaGreen;"><strong>0</strong></span><span style="color: MediumSeaGreen;"><strong>o</strong></span><span style="color: MediumSeaGreen;"><strong>7</strong></span><span style="color: MediumSeaGreen;"><strong>6</strong></span><span style="color: MediumSeaGreen;"><strong>7</strong></span><span style="color: MediumSeaGreen;">;</span> <strong>2</strong> <strong>2</strong><strong> │ </strong> </code></pre>
js
Number.parseInt("-1f7", 16);
<pre class="language-text"><code class="language-text">code-block.js:1:1 <a href="https://biomejs.dev/linter/rules/use-numeric-literals">lint/complexity/useNumericLiterals</a> <span style="color: #000; background-color: #ddd;"> FIXABLE </span> ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ <strong><span style="color: Orange;">⚠</span></strong> <span style="color: Orange;">This call to </span><span style="color: Orange;"><strong>Number.parseInt()</strong></span><span style="color: Orange;"> can be replaced by a hexadecimal literal.</span> <strong><span style="color: Tomato;">&gt;</span></strong> <strong>1 │ </strong>Number.parseInt(&quot;-1f7&quot;, 16); <strong> │ </strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong> <strong>2 │ </strong> <strong><span style="color: lightgreen;">ℹ</span></strong> <span style="color: lightgreen;">Using a literal avoids unnecessary computations.</span> <strong><span style="color: lightgreen;">ℹ</span></strong> <span style="color: lightgreen;">Safe fix</span><span style="color: lightgreen;">: </span><span style="color: lightgreen;">Use the computed hexadecimal literal instead.</span> <strong>1</strong> <strong> │ </strong><span style="color: Tomato;">-</span> <span style="color: Tomato;"><strong>N</strong></span><span style="color: Tomato;"><strong>u</strong></span><span style="color: Tomato;"><strong>m</strong></span><span style="color: Tomato;"><strong>b</strong></span><span style="color: Tomato;"><strong>e</strong></span><span style="color: Tomato;"><strong>r</strong></span><span style="color: Tomato;"><strong>.</strong></span><span style="color: Tomato;"><strong>p</strong></span><span style="color: Tomato;"><strong>a</strong></span><span style="color: Tomato;"><strong>r</strong></span><span style="color: Tomato;"><strong>s</strong></span><span style="color: Tomato;"><strong>e</strong></span><span style="color: Tomato;"><strong>I</strong></span><span style="color: Tomato;"><strong>n</strong></span><span style="color: Tomato;"><strong>t</strong></span><span style="color: Tomato;"><strong>(</strong></span><span style="color: Tomato;"><strong>&quot;</strong></span><span style="color: Tomato;">-</span><span style="color: Tomato;"><strong>1</strong></span><span style="color: Tomato;"><strong>f</strong></span><span style="color: Tomato;"><strong>7</strong></span><span style="color: Tomato;"><strong>&quot;</strong></span><span style="color: Tomato;"><strong>,</strong></span><span style="color: Tomato;"><span style="opacity: 0.8;"><strong>·</strong></span></span><span style="color: Tomato;"><strong>1</strong></span><span style="color: Tomato;"><strong>6</strong></span><span style="color: Tomato;"><strong>)</strong></span><span style="color: Tomato;">;</span> <strong>1</strong><strong> │ </strong><span style="color: MediumSeaGreen;">+</span> <span style="color: MediumSeaGreen;">-</span><span style="color: MediumSeaGreen;"><strong>0</strong></span><span style="color: MediumSeaGreen;"><strong>x</strong></span><span style="color: MediumSeaGreen;"><strong>1</strong></span><span style="color: MediumSeaGreen;"><strong>f</strong></span><span style="color: MediumSeaGreen;"><strong>7</strong></span><span style="color: MediumSeaGreen;">;</span> <strong>2</strong> <strong>2</strong><strong> │ </strong> </code></pre>

Valid

js
parseInt(1);
parseInt(1, 3);
Number.parseInt(1);
Number.parseInt(1, 3);

0b111110111 === 503;
0o767 === 503;
0x1F7 === 503;

a[parseInt](1,2);

parseInt(foo);
parseInt(foo, 2);
Number.parseInt(foo);
Number.parseInt(foo, 2);
</TabItem> </Tabs>